A ball valve generally consists of a ball having an aperture extending therethrough, a first valve seat member positioned on a first side of the ball having a first arcuate valve seat, and a second valve seat member positioned on a second side of the ball having a second arcuate valve seat. When the aperture of the ball is axially aligned with the conduit such the fluid can flow along the conduit through the aperture, the ball valve is said to be in an open position. When the ball is rotated to block the flow of fluid along the conduit, the ball valve is said to be in a closed position. The ball valve assembly includes a valve housing, and means for locking the first valve seat member and the second valve seat member within the valve housing.
When it is necessary to control the flow of fluids through a conduit, a tubular valve housing is incorporated in the conduit. A common means for locking the first valve seat member within the tubular valve housing is to place a shoulder in an interior surface of the tubular valve housing and a corresponding shoulder on the first valve seat member. The first valve seat member is then dropped into place with the shoulder of the first valve seat member engaging the shoulder positioned within the tubular valve housing. The ball is then placed in position on the first arcuate valve seat of the first valve seat member. The second valve seat member is locked in position by placing a first groove and a second groove in the interior surface of the tubular valve housing. The first groove and the second groove mark the position of the first valve seat member. A first split retaining ring is positioned within the first groove, the second valve seat member is placed in position, and then a second split retaining ring is positioned within the second groove. The first valve seat member is confined between the first split retaining ring and the second split retaining ring. An annular retaining ring is usually placed adjacent the second split retaining ring and locked in position by means of a spiral wound retaining ring that is received in a third groove in the interior surface of the tubular valve housing.
The disassembly of the ball valve assembly, as described, requires that the spiral wound retaining ring and the annular retaining ring be removed to allow access to the second split retaining ring. The second split retaining ring can then be removed using a pry bar. The ball is then positioned in an open position and an aluminum bar used to knock the second valve seat member out of the tubular valve housing. Once the second valve seat member is removed the first split retaining ring can then be removed using a pry bar. Once the first split retaining ring has been removed, the ball and the first valve seat member can be knocked out of the tubular valve housing using the aluminum bar.
Problems have been experienced with this type of disassembly with respect to valves used in the oil and gas industry. Through normal use, such valves become encrusted with drilling mud. When the valves are removed and sent for servicing, the mud becomes encrusted on the components of the ball valve assembly making them difficult to remove. The most delicate portion of the disassembly relates to the removal of the second valve seat member. As described above, removal of the second valve seat member requires that an aluminum bar be extended through the aperture in the ball. If great care is not taken the second arcuate valve seat on the second valve seat member can be damaged beyond repair. In many cases it is impossible to dislodge the second valve seat member from the encrusted drilling mud without damaging the second arcuate seat.